By John Kerr 19/09/2017

The global warming limit set at the 2015 Paris Climate Summit is still possible, say scientists, but we need to redouble our efforts if the Earth’s atmosphere is to limbo under the ambitious boundary.

In an article published today in Nature Geoscience an international team of climate scientists reports a re-assessment of complex Earth System Models. Crunching the numbers in light of new data, they have updated estimates the outstanding ‘carbon budget’ – the total amount of carbon humanity could emit and still scrape under the limit of warming by less than 1.5 °C by the end of the century.

We are already well on our way; in 2015 human-induced warming was estimated to be about 0.9 ◦C above mid-nineteenth-century conditions and increasing at almost 0.2 ◦C per decade.

But it’s not time to throw in the towel yet. The authors say that with ambitious mitigation of greenhouse gases, future total carbon emissions as large as 250 to 540 billion tonnes could be compatible with limiting warming to 1.5 °C above pre-industrial temperatures by 2100. To put that in context, 240 billion tonnes is about 20 years’ of current emissions.

Read more about the research on 

The authors, including Prof Dave Frame from Victoria University Wellington, suggest that regular updates of human-induced warming based on a transparent methodology will help countries to adjust their commitment to climate change mitigation.

In the long-term we will need to move well beyond fossil fuel infrastructure as well as actively working to remove more emitted carbon from the atmosphere. The paper states:

Longer-term deep decarbonization also relies on many energy system innovations, including development and deployment on an unprecedented scale of renewable energy as well as, as-yet undemonstrated, amounts of carbon capture and storage and CO2 removal.

Not a ‘geophysical impossibility’

Ultimately the climate scientists behind the paper conclude the ambitious Paris targets are not yet out of our reach:

Our analysis suggests that ‘pursuing efforts to limit the temperature increase to 1.5 ◦C’ is not chasing a geophysical impossibility, but is likely to require a significant strengthening of the [Nationally Determined Contributions] at the first opportunity in 2020 to hedge against the risks of a higher-than-expected climate response and/or economic, technical or political impediments to sustained reductions at historically unprecedented rates after 2030.

Speaking to the Dominion Post, Prof Frame said “this means it’s still possible if we really try. [However] if we really try is a question for politics and economics.”

“The point of it is if we hit the brakes really hard we could do less damage than we thought.”